In order to develop novel fungicides, the structure of flavanane phytoalexins was modified in view of bioisosterism and 23 novel title compounds, 2-heteroaryl-4-chromanones, were designed and synthesized, whose structures were confirmed by ^1H NMR, MS and elemental analyses. The fungicidal IC~5~0 in vitro against rice blast disease of the title compounds were measured and the quantitative relationship between the structures and fungicidal activities was established using the comparative molecular field analysis (CoMFA) approach. The results of 3D-QSAR analysis suggested that the introduction of small steric bulk but strong electronreleasing group onto the 5, 6, 7-position of th ebenzene ring would be favorable to the activity of the compound. The CoMFA analyses about the electronic property requirement of 7-O and 19-O were consistent with those derived from the Hansch-Fujita approach.

Key words: HETEROCYCLIC COMPOUNDS, FUNGICIDES, PYRANONE P, BENZOPYRAN P, ANTITOXINS, QUANTITATIVE STRUCTURE ACTIVITY RELATIONSHIP, FLAVANONE